Text teletype (TTY) devices are often used by people with hearing disabilities to communicate over a network. A typical TTY device has a keyboard, and keystrokes by a user are converted into electrical signals that are sent over the network. The network used to transport the electrical signals may include a packet-based communication network. A typical packet network can support communication sessions between two or more participants. For example, the network could support a voice telephone call by transporting Internet Protocol (IP) packets between a calling party and a called party. In general, codecs are used to process voice signals for transport over the packet network.